Safety device for dynamo electric machines



Jan. 5, 1932. G, E, PLATZER V 1,840,129

SAFETY DEVICE FOR DYNAMO ELECTRIC MACHINES Filed A ril 13, 1929 Inventor: George E .Flatzer,

' yWwZZa Hi5 Attorney.

2W mo-electric machine is coupled with an in- Patented Jan. 5, 1932 UNITED". STATES PATENT OFFICE GEORGE E. PLATZER, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC i COMPANY, A CORPORATION OF NEW YORK' SAFETY DEVICE FOR DYNAMO ELECTRIC MACHINES Application filed April 13,

' This invention relates to the protection of machines designed to operate at high speeds and more particularly to the protection of such machines in systems in which a dynaternal combustion machine for effecting certain testing operations of the latter, and has for an object the provision of a simple, reliable and accurate over-speed protective system the operation of which shall be independent of the field current, generated voltage, or developed power of the dynamo-electric machine.

In illustrating my invention in one form thereof, I have shown it as embodied in a testing system in which a dynamometer is employed for carrying out certain tests on an internal combustion engine, such as an airplaneor an automobile engine, and in which the dynamometer is coupled with the engine undergoing the test for the purpose of converting the mechanical energy develo ed by the engine into electrical energy and elivering vthe same to a consuming device or to a source of electrical supply.

In carryin my invention into effect in one form thereo I provide a tachometer generator arranged to be driven by the dynamometer and to generate voltage proportional to the speed thereof, together with means responsive to a predetermined voltage of the generator for disconnecting the dynamometer from the supply lines and deenergizing the ignition circuits of the internal combustion engine at a predetermined speed of the dy-' namometer. r

For a better and more complete understanding of my invention, reference should now be had to the following specification and to the accompanying drawing, the single figure of which is a simplified, diagrammatic representation of my invention.

Referring now to the drawing, an internal combustion enginelO, such as an airplane engine or an automobile engine, is suitably mounted upon a testing stand 11. The shaft of a cradle dynamometer 12 is mechanicall coupled with the shaft of the engine 10 wit a suitable coupling device as indicated in the drawing. The dynamometer is provided 1929. Serial No. 354,936.

with an armature and with field windings (not shown). A suitable source of electrical supply which maybe the shop mains, repre- 'sented by the numeral 13 on the drawing, is

connected to'terminals of the field circuit of the dynamometer, through the conductors 14 and 15 and the variable resistance 16. Mechanical energy developed by the internal combustion engine 10 is converted into electrical energy in the armature circuit of the dynamometer 12 and is pumped back into the supply lines 13 through the conductors 17 and 18.

A line contactor of any suitable form such as that represented by the numeral 19 in the ,5

drawing, is provided for the purpose of closmg and interrupting the armature circuit of the dynamometer at the proper time. A normally open push button 20 and a normally closed pus button 21 are provided for respectively establishing or interrupting the energizing circuit of the contactor 19. As shown in the drawing, the contactor 19 is provided with main contacts 22 in the armature circuit of the dynamometer and with aux- 7 7 by those skilled in the art, a tachometer generator is an especially designed generator, the generated voltage of which varies in direct proportion to the speed at which its armature member is rotated.

Associated with the dynamometer is a control panel 26 upon which are mounted a tachometer instrument '27 and a control relay 28, the energizing coils of both of which elements are connected to the terminals of the armature member of tachometer generator 24, through the conductors 29 and 30. The setting of relay 28, that is to say the voltage to which the relay 28 may be'made to respond, may be varied by turning an adjustable thumb nut 31 provided for the purpose of varying the air gap between a magnetic member 32 and the core members 33 and 34 of the relay.

Also mounted upon the panel 26 is a control contactor the function of which is to control the energizing circuit oi line contactm' l9 and the ignition circuits of internal combustion engine 10. A start contactor 36, which may be ot any suitable type, but which is indicated in the drawing as a normally open push button, is provided for establishing an energizing circuit from the supply lines 3? to the coil 38. The contactor provided with auxiliary contacts 39 for the purpose of establishing a selfholding circuit for the coil 38 independent of the start push button 36. Likewise, a stop contactor ll) which may be of any suitable type but which tor the purpose of illustration is show in the drawing as a normally closed push button is ])1O7l(l(ll in the selfholding circuit of the coil 38 and serves when depressed to its lower or open position to interrupt the energizing circuit of the contactor 35.

The control contactor 35, as shown in the drawing, is provided with normally open contacts 41 and i2 and with normally closed contacts Normally open contact llis located. in series with the coil of line contactor 19 and must be operated to the closed position before the line contactor 19 can be closed. Similarly, normally open-contactor 42 is connected. in the battery ignition circuit of the internal combustion engine 10 and must be operated to the upper or the closed position before the internal combustion engine can be started. Normally closed contact 43 controls the magneto ignition circuit of the internal combustion engine and when operated to the upper or open position, this contactor removes the ground from the magneto circuit for the purpose of rendering the magneto circuit operative.

lVith the above understanding of the elements comprising my invention and the manner in which they are associated with each other, the operation which will now be described in detail will be readily understood.

Before starting up the testing apparatus, the knob 31, which is provided with graduations correspon ding to the speeds of the dynainometer, should be adjusted by turning the same until the graduation at which it is desired that the protective apparatus should function to shut down the engine undergoing test is opposite the arrow 44:. The control contactor 35 may now be operated to the closed position by depressing start button 36 to bridge its normally open contacts thereby establishing an energizing circuit for the coil 38 of the contactor that may be traced from the left hand supply line 37, over conductor 45, through the contacts of start button 36, thence through the coil 38, and through conductor 1:6 to the right hand supply line 37. In responding to the energization of its coil, contactor 35 moves to the upper or closed position in which position the auxiliary contacts 39 are bridged by the movable bridging member to provide a seltholding circuit for the coil 33 through the normally closed contacts of stop push button ll) independently of start push button 36 which may now be released.

In the closed. position of contactor 353 normally open contact 1-2 is closed thus establish in g the battery ignition circuit for the internal combustion engine 10 whilst normally closed contact 41-3 is new open thcrcl'iy remoy' r; the ground "from the magneto ignition cult for the internal combustion engine.

engine may now be started up by a suitstartcr (not shown), or by ope 'ating mometer as a motor from the suprkers in the art.

To start the engine by utilizing the dynanicnnater 12 as a motor it is only necessary to depress the push button 20 to bridge its normally open stationary contact members, the

l; of which i s to establish an energizing *cuit tor the coil o'l': contactor 19 extending rem upper supply line 13, yer conductor 4L7, through the contacts of push button 20, to and through the coil oi contactor 19, over conductor 13, through contacts ll of control contactor 35, and thence by way of conductor 4:" to the lower supply line 13. Line contactor 19 will now move to the upper position in response to the energization of its coil thereby closing the main contacts :22 in the rmature circuit oi the dynamometer and also closing its auxiliary contacts 23 to tablish a seltholding circuit for the coil of the ccntactor, through the contacts of normally closed push button independently F the normally open contacts of push button w Qch may now be released.

pointed out above the normally open contact 4:1 ot the ignition contactor is included in the energizing circuit of the line contactor if) time preventing the connection of the dynamometer 12 to the source 13 pr or to the establishment of the ignition circuit of the engine 11 and on the other hand insuring the establishment of the ignition circuit of the en, lo 11 prior to the operation 01? the dynanunneter 12 a. motor to start the engine. This insured sequence in the starting operation provides a very important safety feature since it ell'ectually prevents the engine 11 from exhausting charges of an explosive mixture into the exhaust line and thus prevents diastrous explosions that might otherwise occur in the exhaust line due either to the ignition. of these unexploded charges by its own heated exhaust gases following a subsequent establishment of the ignition circuit or by the heated gases of other engines simultaneously und oing a test in the laboratory and exhausting into the same line.

After the engine has been started by the pumped into the supply lines 13 by the dynamometer 12 as is well understood by those skilled in the art. The speed at which the rotor of the dynamometer is rotated which is also the speed at which the internal combustion engine 10 is running may be directly observed upon the tachometer 27. Should either the field or the armature circuit of the dynamometer fail thus causing the speed of the internal combustion engine 10 to increase unduly or should the speed of the internal combustion engine 10 for any reason exceed the permissible value, the control relay 28 will respond to the increased voltage generated by the tachometer generator 24 and will attract its armature member 50 against the bias of its spring 51 to the upper position in which the contacts 52 will be closed to establish a short circuit about coil 38 of control contactor 35, through a resistance 53 which is provided toprevent a short-circuit to the supply lines 37. The short-circuit resulting from the closing of contacts 52 is suflicient, however, to deprive coil 38 of the current necessary to maintain the contactor 35 in the closed position. Therefore, contactor 35 will drop to the lower position in which position contact 41 will open and deenergize the line contactor 19 permitting it in turn to open and disconnect the armature of dynamometer 12 from the supply lines 13. Likewise, contact 42 will be opened and the battery ignition circuit of the internal combustion engine 10 will be deenergized Whilst contact 43 will be in the closed position in which the magneto ignition circuit of the eugine 10 will be grounded.

This invention is particularly advantageous in the event that the dynamometer is run as a motor for the purpose of taking friction losses of the internal combustion engine immediately after a high speed low horsepower test with the dynamometer operating as a generator, with reduced field. Should the operator fail to increase the field before operating the dynamometer as a motor, it will be prevented from attaining a dangerous speed with disastrous results.

Although I have described my invention as comprising specific elements associated with each other in a particular manner and as opcrating in a specific way, I would have" it distinctly understood that the invention is nowise limited to the particular elementsdisclosed for the purpose of illustration, nor to the specific connections since persons skilled in the'art will be able to make alterations and changes without departing from the spirit of my invention. v

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In a testing system for an internal combustion engine provided with an ignition circuit, a main dynamo electric machine driven by said engine, and provided with an armature circuit, a contactor for connecting said armature circuit with a source of supply, a second contactorfor controlling the operation of said first contactor and for controlling said ignition circuit, and means including an auxiliary dynamo electric machine for generating an electromotive force proportional to the speed of said main dynamoelectric machine forcausing said second contactor to render said ignition circuit inactive and to cause said first contactor to open said;

armature circuit when the speed of said main dynamo electric machine reaches a predetermined value.

2. A control system for an internal combustion engine provided with an ignition cir-i cuit comprising a main dynamo electric machine having an armature circuit, means ino cluding a contactor for connecting said armature circuit to said source, means including a second contactor for controlling said ignition circuit and having a-normally open contact in the energizing circuit of said first mentioned contactor to prevent the establishment of said armature circuit prior to the establishment of said ignition circuit, andmeans including an auxiliary dynamo electric machine for responding to a predetermined speed of said main dynamo electric machine to cause said contactors to deenergize said armature and ignition circuits.

3. In a testing system for an internal combustion. engine provided with an ignition circuit, a dynamometer mechanically connected to said engine and provided with an armature circuit, means including a contactor for controlling the connection of said armature cir-- speed of said dynamometer to cause said contactors to deenergize saidarlnature and ign-ition circuits.

4. In a testing system, an internal combustion engine provided with a battery and mag neto ignition circuits, a dynainonieter connected to be driven by said engine, a supply line and a contactor arranged when energized to connect the armature of said dynainometer with said supply line,

a second contaetor for controlling the-energization of said first contactor and said battery and ignition circuits, a tachometer generator driven by said engine and arranged to generate a voltage proportional to the speed thereof, and control relay adjustable to respond to a predetermined voltage to control said second contactor to open said battery circuit and ground said magneto circuit, and to deenergize said first contactor at a predetermined speed of said engine.

In witness whereof, I have hereunto set my hand this 12th day of April, 1929.

GEORGE E. PLATZER. 

